A major, critical bug and possible security threat has been discovered in Ubuntu Breezy. Apparently, the 'root' password (not actually the root password because Ubuntu uses sudo) gets written into the installer's log files in clear text, and can be read by any account on the Ubuntu machine. The bug was first discovered and reproduced on the Ubuntu forums. The bug does not seem to affect Dapper, however, users upgrading from Breezy to Dapper might still be at risk because the log files are not modified. Update: Bug is fixed. Please upgrade.

Ubuntu does not let you know the password for the 'root' user ( the real root password ) so that the beginner user cannot log in as root and do some damage. However, ubuntu enables the user which installs the system to use the 'sudo' command which allows the execution of commands as the root user (this is done to avoid using the root account unless when really needed, for example when installing new packages). To use the sudo command you will have to use your user password (the one you decided at install time). This one is the password which is available in clear text.

So, as you can see, the effect is the same even if it isn't the root password.